In the following pages, we intend to analyse the trajectory of the MIR (Revolutionary Left Movement) from its initial genesis in 1965 to its disappearance at the end of the 1980s. In order to approach this time period, we will follow a chronological approach, with the aim of pointing out the distinctive features and the factors that conditioned its development. The main idea guiding this chapter is that the constant feature of the MIR during its existence was the adoption of excessively voluntarist policies based on an idolatry of revolution implemented through armed struggle, ruling out any other alternative. This modus operandi, present in its founding principles, gradually intensified after the establishment of the Pinochet dictatorship, and was reflected in two specific events. The policy of refusing asylum and “Operation Return”. In both cases, it carried out an erroneous analysis of the real scenario, which was likely to result in an overestimation of its capabilities and an underestimation of the adversary’s forces.